1. Field of the Invention
The present invention relates to a fuel vapor separator used in a fuel delivery system of a marine engine for preventing fuel spills when the engine is tipped sideways.
2. Related Art
Small outboard marine engines are usually detachably mounted to the transom of a boat. These engines typically include an integrated fuel system which draws liquid fuel under suction from a can or tank in the boat. The fuel is routed through a vapor separator unit to condense or discharge vapors and then delivered at high pressure to a fuel injection system.
Fuel vapor is a long recognized issue in the marine fuel industry. The fact that fuel is withdrawn from the tank at negative pressure is a main factor. Boat safety regulations require that fuel routed between tank and engine be sucked under a vacuum. This prevents fuel spilling into the boat should the fuel line rupture. However, at such low pressures, the fuel readily vaporizes. This, combined with the high temperatures and jarring conditions, leads to a threat of vapor lock.
Vapor separators are designed to address this excessive vapor issue. In addition to the naturally arising vapors from the vacuum drawing step, heated fuel from the fuel rail is returned to the vapor separator where fuel vapors are condensed back to liquid before the fuel is re-introduced to the high pressure pump and fuel rail. As needed, fuel vapors can be vented to atmosphere or pulled into the engine intake system through a vacuum line connection.
The vapor vent system in most marine vapor separators includes a float activated valve for automatically closing the vent line whenever the fuel level in the separator rises above a predetermined level. This valve prevents liquid fuel from being sucked into the engine through the vacuum line. Additionally, the valve mechanism is designed to close the vent line when the engine is tipped so that liquid fuel does not, through gravity, drain out the vacuum vent line.
Vapor vent valve arrangements in the prior art are commonly constructed according to the float and needle valve principle, in which a buoyant float is supported just below the vapor vent line and connected to a needle valve which closes when the liquid fuel in the vapor separator lifts the float. A typical prior art vent valve system is depicted in FIG. 4. These floats are commonly carried on a pivot pin, with the rotational axis of the float pivot being oriented parallel relative to the pivotal axis of the engine mounting bracket so that the float will close the vent passage whenever the engine is rotated to a tilt (i.e., prop out-of-water) condition. This is important so that liquid fuel does not run out of the engine when it is shut off and tilted into the boat.
Smaller outboard marine engines are often light enough to be manually removed from the boat after use and stored on a trailer, in a vehicle trunk, or perhaps the bed of a pick-up truck. If the outboard marine engine is laid on its side, which would be the intuitive method so as to protect the prop and tiller arm, the pivotal axis of the vent valve mechanism is not likely to permit closure of the float valve. As a consequence, it is possible for liquid fuel to leak from the engine into the vehicle. Accordingly, it would be desirable to have an improved fuel vapor separator in which the vent control device can accommodate engine tippage in non-conventional directions.
Vapor separators are not used in automotive applications because the factors which produce excessive vapors in marine applications are not present. Some automotive emission systems incorporate a so-called “roll-over” vent valve into the fuel tank. However, these systems are passive features of the emission system that simply protect the open vent line to the vapor collection canister. The automotive engine will continue to operate unaffected and without interruption if this roll-over vent valve is disabled or removed. Not so in marine fuel systems, where the vapor vent valve is an active component which will disable the entire engine if not functioning properly. An additional distinction between marine and automotive applications of vapor vent valves is in what they are intended to protect. Automotive roll-over vapor vent valves protect tippage of the fuel tank, whereas marine vent valves protect tippage of the engine-mounted vapor separator.